This invention relates to a mirror scanning control mechanism in a variable magnification type copying machine the magnification factor of which can be changed (increased or decreased).
In a conventional variable magnification type copying machine of this type, the range of enlarging and reducing magnification factors is generally limited as shown in FIG. 1(a). With such a conventional copying machine, a copying operation from one standard size to another standard can be carried out, for instance standard size "A4" can be enlarged into standard size "A3" (the magnification factor being 1.414.times.), and standard size "A3" can be contracted into standard size "A4" (the magnification factor being 0.707.times.), or standard size "A3" can be contracted into standard size "B4" (the magnification factor being 0.813.times.) during the copying operation. However, when the size of an original is not one of the standard sizes as indicated by the point P in FIG. 1(a), its available copying sizes are as indicated by the points P', P" and P'" depending on the magnification factors, because the enlarging or contracting magnification factor is limited as described above. Therefore, it is impossible to increase or decrease the size of the original to a desired standard size. Even if the size of the original could be increased or decreased into the desired size in the copying operation, the image of the original would not be suitable in size with respect to the size of a copying sheet, i.e., the length-to-width ratio of the copying sheet may not be the same as that of the original. Accordingly, sometimes blanks are formed on the copying sheet, or in one dimension the image of the original is too large to be copied on the copying sheet.
This drawback is caused by the fact that the scanning operation of a full-speed mirror having a light source adapted to illuminate an original in a scanning mode, and the scanning operation of half-speed mirrors adapted to transmit to a zoom lens magnification varying device light reflected from the original which is transmitted thereto from the full-speed mirror, are carried out by a speed changer which is driven by a motor rotating only at a constant speed and which has a limited number of speed changes.